Telephone system



July ll, 1939. H, HQVLAND 2,165,855

TELEPHONE SYSTEM Filed Nov. 6, 1957 3 Sheets-Sheet lV I f a@ 22 @il jnw i@ MANUAL 0F F ICE OPERTOR'S MARC/NA L /N VEN TOR h'. HOV/ AND y A T rom/5 V July 11, 1939. H. HovLAND 2,165,855

TELEPHONE SYSTEI Filed Nov. 6, 1937 3 Sheets-Sheet 2 Pomp/25o .w nam/41.

/A/l/ENTOR H. HO VLA ND 1l. l'939 H. HVLAND 2,165,855

TELEPHONE SYSTEM Filed Nov. 6, 1937 3 Sheets-Sheet 3 /Nl/ENTOR H. HO VLAND A 7- TOR/VE V Patented July 11, 1939 UNlTE STATES PATENT GFFIQE TELEPHONE SYSTEM Application November 6, 1937, Serial No. 173,142

8 Claims.

This invention relates to telephone systems and particularly to systems which include both manual and dial offices.

It is the object of the invention to facilitate 5, the transmission of both voice and supervisory signals through an intermediate office on calls between a manual oiiice and a dial office.

Heretofore two-way trunk circuits have been provided for interoflice traffic between manual and dial offices, a marginal relay being provided at the dial office end of a two-way trunk for receiving supervisory signals yfrom the manual office and a polarized relay being provided in the manual oiilce for receiving supervisory signals from the dial ofce. These trunk circuits have been arranged for either local or toll grade transmission. This invention is .a two-way trunk circuit at an intermediate office for connecting a manual ofce with a dial cnice; the circuit com- 20 prises means for repeating impulses from the manual to the dial oflice, a telephone repeater for repeating voice currents in both directions, and means for repeating polarized supervisory signals from the dial to the manual office and for repeating marginal supervisory signals from the manual oflice to the dial office.

A feature of the invention is a two-way trunk circuit at an intermediate office for connecting a trunk from a manual office with a trunk. from a 30 dial oiiice, a high resistance bridge normally connected across the trunk outgoing to the dial office being changed to a low resistance bridge upon seizure of the trunk from the manual office by an operator inthe manual ofce, the maintenance of the low resistance bridge being controlled over the trunk from the dial oflice after the trunk from the manual oiice is released in the manual oflice.

The drawings which form a part of this speci- 4 cation show schematically a telephone system in which the invention is embodied; and a clear an-d complete understanding of the invention may be obtained from the following description of this system. It is, however, understood that the invention is not limited in` its application to the particular system herein disclosed but is generally applicable to systems comprising both dial and manual offices.

Referring to the drawings:

Fig. 1 shows a manual office comprising a line Ll, an operators cord circuit C, and a two-way trunk circuit Tl;

Fig. 2 shows an intermediate office comprising a two-way trunk circuit T2 and an associated two-way telephone repeater; and

Fig. 3 shows a dial oice comprising the twoway trunk circuit T3, incoming selector IS, connector CI, first selector Si, line nder LF, .and subscribers lines L2 and L3.

The manual oice is shown as being a local oflice, the line Li being a local subscribers station and the cord C being a local operators cord. This oflice may, however, be a toll oice, the line LI being a toll line, in which case a toll operators cord is provided and the trunk circuit TI is arranged for use with such a cord. Each trunk circuit such as TI terminates in one or more jacks J2 for completing calls incoming from and outgoing to the dial oil-ice. One or more jacks DJ are provided for connecting the operators dial D to the trunk. The intermediate office may be either a toll or local office and comprises either manually oi automatically operated switching equipment. The two-way trunk circuit T2 at the intermediate oflice is shown as directly connecting a trunk from the manual ofce with a trunk from the dial ofce; but manually or automatically operated switches could be included in this connection. The telephone repeater associated with trunk circuit T2 is of conventional type comprising hybrid coils HCl and I-ICZ and two one-way thermionic amplifiers. The conductors 4| and 42 of the trunk from the manual oiiice are connected through repeating coil RC2 to the hybrid coil HCI and the conductors 51 and 58 of the trunk from the dial ofiice are connected through repeating coil RC3 to hybrid coil HG2; and the balancing networks NE and NW are connected through repeating coils RC4 and RC5 to hybrid coils HCl and HG2. To prevent singing, the repeating coils RC3 and RC5 are normally short-circuited at the back contacts of relay 48. The selector, connector' and line nder switches in the dial office may be of the well-known two-motion step-by-step type; for a description of such switches and their operation reference may be had to the second edition of Automatic Telephony by Smith and Campbell, pages 52 to 65, inclusive, and to Patent No. 1,799,654 granted to R. L. Stokely, April '7, 1931. Each of the switches IS, Si .and LF is represented by a set of brushes and a single set of terminals; the magnets, relays and other associated apparatus are represented by the broken lines leading to the brushes of these switches. The connector Ci is represented by a set of brushes and a single set of terminals, the line relay 9i, the release relay 92 and the supervisory relay 95; all other relays and operating magnets are represented by the broken lines.

Consider first the operation of the Various circuits on a call originating in the manual oice over line LI. The call is answered by inserting the plug Pl in jack J l, key KI being operated to complete the talking connection between line LI and the operators telephone circuit I5. Relay I operates in a circuit through lamp I3 and the sleeve of jack J I Relay II opens the connection between the lower and middle windings of relay I2 and closes a circuit through the lower and upper windings of relay i2 and the line LI. Relay I2 operates, closing a locking circuit for relay Il which shunts and thereby prevents the lighting of supervisory lamp I3. If the called subscribers station is in the dial office, plug P2 is inserted in the jack J2 of an idle trunk TI. A circuit is thereby closed through the winding of relay lli, lamp I9 and the sleeve of jack J2 for operating relay Il and lighting lamp I9. Relay Il opens the connection between the middle and lowei` windings of relay I8 and closes a circuit for operating relay 2| of trunk circuit TI this circuit is traced from battery through the lower front contact of relay I'I, lower winding of relay I8, ring conductors of plug P2 and jack J2, lower left winding of repeating coil RCI, both windings of relay 2|, upper left winding of repeating coil RCI, tip conductors of jack J2 and plug P2, and through the upper winding of relay I3 to ground at the inner upper front contact of relay Relay 2| operates but the resistance of its lower winding is high enough to prevent the operation of the marginal supervisory relay I8. The operation of relay 2| closes circuits for operating relays 22 and 23, thereby preventing the lighting of line lamp 24 which is associated with jack J 2 of trunk circuit TI. At its upper front contact, relay 22 short-circuits the lower high-resistance winding of polarized relay 25. Both windings of relay 25 are normally connected in series with the right windings of repeating coil RCI, conductors 4| and 42 of the trunk to the intermediate office, the left windings of repeating coil RC2, conductors 43 and 44, and the windings of marginal relay 45 of trunk circuit T2, the resistance of the lower winding of relay 25 being high enough to prevent the operation of relay 45 and the direction of current being in the non-operate direction as regards relay 25. When,` however, relay 22 short-circuits the lower winding of relay 25, the current over trunk conductors 4| and 42 is increased sufliciently to cause the operation of relay 45 of trunk circuit T2 in the intermediate ofllce. Relay 45 closes a circuit for operating the slow-to-release relay 46. Relay 45 connects resistor 52 in parallel with the winding of relay 59 and closes a circuit for operating relay 48. Resistor 52 prevents the false operation of relay 5i) during the transmissio-n of dial impulses as hereinafter described; and relay 48 opens the short circuits across the repeating coils RC3 and RC5. Normally there is a bridge, comprising the right windings of repeating coil RC3, the windings oi polarized relay 55 and a high resistance 54, connected across conductors 51 and 58 of the trunk to the dial office and in series with the windings of the line relay v(not shown) of the associated incoming selector IS in the dial oflice. The current in this normally closed circuit is insufficient to operate the line relay of the selector and is in the non-operate direction as regards relay 55. When relay 45 operates in response to seizure of the trunk circuit TI in the manual olice, as hereinbelore described, the upper front contact of relay 45 short-circuits the high resistance 54, thereby increasing the current over conductors 51 and 58 suflciently to cause the operation of the line relay of the incoming selector IS, ground potential being thereupon connected to sleeve conductor 713 in usual and well-known manner to guard against seizure of trunk T3 by any selector, such as SI, in the dial oi`n`ce. Dial tone is transmitted from the incoming selector over conductors 5l and 53, through repeating coil RC3, telephone repeater, repeating coil RC2, over conductors 4| and 42 through repeating coil RCI to the calling operator in the manual oce. The operators vdial D is connected through plug 39 and dial jack DJ across conductors 4| and 42, relay 25 being disconnected from these conductors While the called subscribers number is being dialed. Relay 45 alternately releases and reoperates in response to each of the impulses created by the operation of the dial D. Being slow in releasing, relay 46 does not release during the response of relay 45 to dial impulses. The release of relay 45, in response to the first impulse of each train, closes a circuit for operating relay 4l. Relay 4l is a slow-to-release relay and remains operated during the response of relay 45 to each train of impulses. The operation of relay 4l releases relay 48 so as to close the short circuits across repeating coils RC3 and RC5 during the transmission of dial impulses. At its upper contacts relay 4l short-circuits the bridge comprising the right windings of repeating coil RC3 and the winding of relay 50 in parallel with resistor 52. The resistor 53 is connected across conductors 5l and 58 to make the resistance of the impulse transmitting circuit meet the requirements for ecient impulse transmission to all of the step-by-step switches through which the connection is extended. At its upper contacts, relay 45 repeats the dial impulses received from the dial D over the conductors 51 and 58 to the line relay of the incoming selector IS. The brushes of selector IS are thereby advanced to select the required group of trunks and to hunt for and seize an idle trunk therein. After this selector has seized an idle trunk in the selected group, the impulse repeating circuit over trunk conductors 51 and 58 is extended to the line relay 9| of a connector switch CI. Relay 9| closes a circuit for operating relay 92, and relay 92 connects ground to sleeve conductor 93 and thence to the sleeve conductor I3 to guard trunk T3 against seizure on a call originating in the dial oflice. The connector switch CI is selectively operated in response to the last two digits of the called subscribers number to establish connection with the line L2 of the called station B. If the called station is idle, ringing current is transmitted to operate the ringer at station B in usual manner and, when the call is answered, relay 95 operates reversing the current over conductors 1| and l2 to cause the operation of polarized supervisory relay 5U of trunk circuit T2. Relay 50 closes a circuit for operating relay 5I, thereby reversing the current over conductors 4| and 42 to cause the operation of polarized relay 25 of trunk circuit TI in the manual ollice. Relay 25 closes circuits for operating relays 26 and 2l. Relay 2l closes a locking circuit for relay 23 so as to prevent the lighting of lamp 24 in case the calling operator disconnects and relay 25 is being alternately operated and released by a line or trunksbusy signal. At its upper front contact relay 25 short-circuits the lower, high resistance, winding of relay 2| thereby increasing the current through the windings of the calling supervisory relay I8 sufficiently to cause its operation. The operation of relay IB short-circuits and thereby extinguishes the calling cord supervisory lamp I9 to indicate to the operator that the called station has answered. Ii the called line is busy or the selector IS nds all connectors busy in the selected group, a busy tone is transmitted to the calling operator by intermittently reversing the current over conductors 51 and 58. The supervisory relays dil, 25 and i8 are thereby alternately operated and released to flash lamp I9.

When the calling operator removes plug P2 from jack J2, relays il, I8, 2l and 22 release; but relay 233 is held operated under control of relay 2l. With relay 22 released, battery is connected through resistor 28, the inner lower iront Contact of relay 25 and the inner lower back contact of relay 22 to the sleeve of jack J2 to make the trunk Ti test busy. The releaseof relay 22 opens the short circuit across the lower winding of relay 25, thereby causing the release of relays dii and il@ of trunk circuit T2 at the intermediate office. With relays @'55 and it released, the high resistance tie is again connected in series with the Winding of relay 5t across trunk conductors el' and 58, thereby causing the release of relays Si and 92 of the connector CI. The release of relay 92 disconnectsI ground from sleeve conductor $3, causing the return of selector IS to normal in usual and well-known manner. When the called subscriber returns the instrument to normal, relay t5 releases and the connector switch Cl is returned to normal in usual and well-known manner. When the selector IS returns to normal, relays 5t and 5! of trunk circuit T2 are released. The release of relay 5i causes the release of relays 25, 25, 2l and 23 of trunk circuit TI. Release of relay 2G disconnects the guarding potential from the sleeve of jack J2.

On a call from the dial office to the manual oiiice, the line L3 of a calling station such as E is connected by the operation of a line nder switch LF, to a rst selector Si. The selector Si respends to the dialing of the first digit of the called number to select an idle trunk such as T3. Upon extension of the connection lthrough switches LF and SI to the trunk T3, relay 6I operates- Relay Eil closes circuits for operating relays 62 and 63. Relay 62 closes a circuit for operating relay tit, connects ground to conductor 'lil to operate an alarm circuit in case a permanent signal condition exists, and connects ground to conductor 'i3 to hold the switches Si and LF, and to guard the trunk T3 against seizure by another flrst selector. Relay t3 closes a circuit for operating relay Eid, Relay 6d locks under control of relay t2 and connects trunkconductors 5l and 5S to the windings of marginal relay S5, thereby causing the operation of polarized relay 5e of trunk circuit T2. Telay 5i) closes the circuit for operating relay 5 i. Relay 5i reverses the current over conductors fil and 42, thereby operating relay 25 of trunk circuit TI in the manual office. Relay 25 closes the circuits for operating relays 26 and 2l. Relay 26 closes the circuit for lighting 'trunk lamp 24. A ringing signal is given the calling subscriber by connecting the ringing source 58 through contacts ci relays t5 and 66, and condenser t@ to conductor 32.

When the call is answered, by inserting a plug Pi in jack J2, relays Il, l2, 2|, 22 and 23 operate. Lamp 261 is extinguished and lamp i3 is not energized. Operation o key Kl to the talking position completes the connection between the operators telephone circuit It and the calling station E in the dial oice, and the operator iurther extends the call as required, for instance, by inserting plug P2 in the jack J l of a subscribers line. The operation of relay 22 short-circuits the lower winding of relay 25, to cause the operation of marginal relay 'i5 of trunk circuit T2. Relay t5 closes the circuit for operating relay et; and closure of the low resistance bridge across conductors 5l and 53 causes the operation of marginal relay 65 of trunk circuit T3. Relay te thereupon releases, opening the ringing tone circuit; and relay 51 operates to reverse 'the current over conductors 8l and 82. The talking connection includes condensers B.

If the answering operator disconnects before the instrument is returned to normal at the calling station E, relays il, I2, 2| and 22 release but relay 23 is held by relay 2l' to prevent lighting lamp 2li. When the instrument at station E is returned to normal, relays @l and et release but relay t2 is held operated under control oi' relay 65. The release of `relay 63 reverses the current over conductors 5l and 53, to cause the successive release of relays 5l), 5l, 25, 2l and iii, thereby lighting lamp it as a disconnect signal. As soon as the plug PI is disconnected from jack J 2, relays ii, 2|, 22, 23 of trunk circuit Ti release, The release of relay 22 opens the short circuit around the lower winding of relay 25, thereby causing the release of relays l5 and e5 of trunk circuit T2. The release of relays 25 and it changes the bridge across trunk conductors 5l' and 5t to include the high resistance till, thereby causing the release of relays 65, 61, 62 and B of trunk circuit T3. The release of relay (i2 disconnects the guarding ground potential from conductor 'it so Vthat trunk T3 may again be selected for use on a call originating in the dial oilce.

What is claimed is:

1. In a telephone system, a manual office, a dial office, an intermediate ofce, and a two-way trunk circuit at said intermediate omce connecting said manual and dial oilices, said trunk circuit comprising means for repeating talking current, means for repeating selective impulses to the dial ofce, and means for repeating supervisory signals in both directions.

2. In a telephone system, a trunk circuit interconnecting a manual oihce and a dial office, means in said trunk circuit for amplifying and repeating voice currents in both directions, means in said trunk circuit for repeating selective signals from said manual oilice to said dial office, means in said trunk circuit for repeating marginal supervisory signals from the manual office to the dial office, and means in said trunk circuit for repeating polarized supervisory signals from the dial oflice to the manual oilice.

3. In a telephone system, a manual oflice, a dial cnice, means comprising a two-Way trunk circuit in said manual orce, a two-way trunk circuit in said dial office, and a two-way trunk circuit at an intermediate point for use in connecting a calling line in either of said oices with a called line in the other of said oiices, said intermediate two-way trunk circuit comprising means for amplifying and repeating talking current in both directions, means for repeating selective signals from the manual office to the dial oflice, and means for repeating supervisory signals in both directions.

4. In a telephone system, a manual office, a dial office, a two-Way trunk circuit in said manual oice for use in completing calls to and from said dial office, a two-way trunk circuit in said dial Office for use in completing calls to and from said manual oice, another two-way trunk circuit interconnecting the first-mentioned twoway trunk circuit with the second-mentioned two-way trunk circuit, means in said trunk circuits for transmitting selective impulses from the manual oiiice to the dial oice, means in said trunk circuits for transmitting voice currents in both directions, means in said trunk circuits for transmitting marginal supervisory signals from the manual to the dial ofce, and means in said trunk circuits for transmitting polarized supervisory signals from the dial to the manual office.

5. In a multi-cnice telephone system, a twoway trunk circuit in a first office, a two-Way trunk circuit in a second oce, another two-Way trunk circuit interconnecting the rst-mentioned two-way trunk circuit with the second-mentioned two-Way trunk circuit, means in each of said trunk circuits for repeating voice currents from a line in either one of said oiiices to a line in the other of said ofces, means in the rst-mentioned trunk circuit for transmitting selective signals and marginal supervisory signals to the third-mentioned trunk circuit, means in the second-mentioned trunk circuit for transmitting polarized supervisory signals to the third-mentioned trunk circuit, and means in the thirdmentioned trunk circuit for repeating the selective signals received from the first-mentioned trunk circuit, and for repeating the supervisory signals from each of the mst-mentioned and second-mentioned trunk circuits.

6. In a telephone system, a manual oice, a dial cnice, an intermediate oiiice, and means comprising a trunk between said manual and intermediate offices, a trunk between said dial and intermediate oflices, and a two-way trunk circuit at said intermediate office for connecting said manual and dial oflices, said trunk circuit comprising a high resistance bridge across the trunk to the dial office, means responsive to seizure of the rst-mentioned trunk by an operator in the manual cnice for changing said high resistance bridge to a low resistance bridge, and means controlled over the trunk from the dial oflice for maintaining said low resistance bridge after the operator releases said iirst-mentioned trunk.

'7. In a telephone system, a manual oflice, a dial oiice, a trunk circuit in said manual oice, a trunk circuit in said dial oice, and a trunk circuit interconnecting the iirst-mentioned and second-mentioned trunk circuits, each of said trunk circuits being arranged to repeat voice currents in both directions, the first-mentioned trunk circuit being arranged to transmit selective signals and marginal supervisory signals to, and receive polarized supervisory signals from, the third-mentioned trunk circuit, the secondmentioned trunk circuit being arranged to transmit polarized supervisory signals to, and receive marginal supervisory signals from, the thirdmentioned trunk. circuit, and the third-mentioned trunk circuit being arrang-ed to repeat selective signals and marginal supervisory signals from the rst-mentioned trunk circuit to the second-mentioned trunk circuit and to repeat polarized supervisory signals from the secondmentioned trunk circuit to the first-mentioned trunk circuit.

8. In a telephone system according to claim '7, means in said third-mentioned trunk circuit for amplifying the voice currents.

HENRY HOV'LAND. 

